This invention relates to a machine vision seam tracking method and apparatus for welding robots, and, in particular, to an apparatus which can automatically correct the welding path to adapt to the deviation between the actual welding seam and the taught path caused by the dimensional tolerances of workpieces or positional errors of fixtures so that the taught path can be corrected to align with the actual welding seam.
Recently, welding robots have been widely utilized by people in the welding field. However, conventional welding robots can only follow the taught path to affect the welding operation, thus their functions are limited. In other words, conventional welding robots respond only in accordance to given positional data. Under such circumstances, we have to strictly demand the reproductiveness of the welding robot itself as well as the precise matching between the dimensions of the workpiece and the positioning of the fixture, if we expect the welding robot to function well in the production line. Therefore, the operational cost of the conventional welding robot will be relatively increased.
Accordingly, it is desirable to provide a visual seam tracking apparatus which can be mounted on a welding robot to affect the welding operation with desired precision without increasing the production cost therein.
A vision system utilizing an electronic photographic means has been applied to the tracking of the welding seam. There are two basic types: off-line and on-line. The off-line system involves both seam tracking and information correcting procedures prior to the welding operation. The on-line system ensures that the tracking and welding operations are simultaneous. However, up to now, the known tracking apparatus only utilizes the laser as a light source, which may increase the cost as well as cause a hazard (The direct projection of a laser into the human eye may cause blindness). Further, calibration and maintenance of the laser source also cause inconvenience.
It is, therefore, preferable for us to provide a common light source instead of a laser source to affect the tracking of the welding seam.